1. Field of the Invention
The present invention relates in general to force-sensitive transducers and in particular to a load sensing probe for measuring the work forces present in a machine tool.
2. Description of the Prior Art
The ability to measure force or load is a vital part of many industrial processes. Recognizing that a structure undergoes a dimensional change when subjected to a load, a measure of the dimensional change in a structure can accurately indicate the amount of load or force applied thereto. Such measurement is usually made through the use of a wire, foil, or semiconductor element intimately bonded to the structure. By measuring the change in the electrical resistance of the element, which resistance is a function of the change in cross-section of the element due to alterations in the dimensions of a structure, it is possible to accurately measure the load applied to the structure.
Many transducer devices have been developed for attachment to structures for measuring the amount of stress applied thereto. U.S. Pat. Nos. 3,444,390 to Breidenbach et al. and 4,171,646 to Dybel et al. both disclose measuring devices for use on machine tools such as forges, presses, and the like. Generally, such prior art devices are not sufficiently sensitive or physically constructed to be readily adaptable for use in areas of a machine near the tool in order to directly measure forces on the tool. For example, the transducer arrangements disclosed in the above-mentioned patents are incapable of directly measuring the working load on a tool. This inability to directly measure tool loading is a particularly acute problem when it is desired to monitor the individual loads on a plurality of tools carried on a common base and caused to do work simultaneously.
Ideally, the apparatus for measuring the work forces in a machine tool may be mounted substantially or totally within a machine so that it is protected from physical damage resulting form inadvertent impact or from contamination by debris or lubricants. It is also desirable that the load measuring apparatus be accessible for removal, inspection, maintenance, or repair.